Dystonia musculorum deformans: Analysis with electromyography

Abstract

Dystonic movements and postures were analysed with surface electromyography in idiopathic dystonia musculorum deformans. Involuntary muscular contraction occurring in the recumbent posture, on standing, and responses to passive stretch and isometric voluntary contraction were observed in neck, trunk and extremity muscles and the results are summarized as follows: 1. (1) Tonic non-reciprocal, involuntary activity appeared in agonists and antagonists. This dystonia was directly stimulated by postural effort, such as attempted sitting or standing, or by attempted voluntary movement. 2. (2) Regular or irregular grouping of action potentials appeared in the EMG in most cases in which synchronous activity among different muscles is characteristic. 3. (3) Simple voluntary contraction developed smoothly in spite of the dystonic disorder. Weakness and disorders of reciprocal innervation were observed in some muscles. 4. (4) Regular grouping of action potentials at around 10 c/sec appeared frequently on voluntary contraction. 5. (5) Passive stretch of dystonic muscles, at stages of the disease preceding absolute fixity of posture, seldom provoked or increased tonic contraction reflexly. The response to stretch was indirect, either as a paradoxical reaction of Westphal (contraction of antagonist muscles), or as a delayed enhancement of dystonia. The pattern of response to stretch was related to the duration of dystonia in the muscles concerned, being more labile when the development of dystonia had been recent. These findings are discussed in relation to athetosis, symptomatic dystonia and dystonia in flexion.